Field of the Invention
The present invention relates to an outboard motor, and more particularly, to an outboard motor preferably employed in a ship model having an engine provided with a catalytic converter.
Description of the Related Art
An outboard motor mounted on a small boat and the like is configured such that an upper unit and a guide exhaust are connected to an upper portion of a lower unit provided with a propeller, an engine is supported and fixed on the guide exhaust, the engine is covered by an engine cover, and the propeller is rotated and driven by the engine. An exhaust gas from the engine is discharged to the seawater through an exhaust passage vertically provided on the side surface of the engine across upper and lower units. In such an engine of the outboard motor, a catalytic converter may be provided in the exhaust passage in order to purify the exhaust gas and comply with an exhaust gas control requirement in some cases.
For example, in Patent Document 1, there is discussed an outboard motor engine having a crankshaft arranged vertically, in which an exhaust passage communicating with an exhaust port is formed in the side surface of the engine, and a catalyst is arranged in parallel with a flow of the exhaust gas.
In such a type of outboard motors, output power may be differently set under the same basic engine configuration in some cases. In addition, a specific level of the exhaust gas control requirement may be differently established depending on nations or regions. Therefore, it is necessary to change a configuration of the catalytic converter depending on nations or regions under the same engine configuration. Furthermore, in some cases, there is a demand for sharing of the engine between a catalyst-mounted model and a non-catalyst-mounted model. Conventional outboard motors are not easy to satisfy such a demand.